Deprotonation in mixed-valent diiron(II, III) complexes with aniline or benzimidazole ligands

Eric Gouré (1, 2) , Michaël Carboni (1, 2) , Angélique Troussier (1, 2) , Patrick Dubourdeaux (1, 2) , Martin Clémancey (1, 2) , Nathalie Gon (1, 2) , Ramachandran Balasubramanian (1, 2) , Colette Lebrun (3, 4) , Jacques Pécaut (3, 4) , Geneviève Blondin (1, 2) , Jean-Marc Latour (1, 2)

1 Laboratoire de Physicochimie des Métaux en Biologie, Département de Biologie Moléculaire
2 LCBM - UMR 5249 - Laboratoire de Chimie et Biologie des Métaux
3 SCIB - UMR E3 - Service de Chimie Inorganique et Biologique
4 RICC - Reconnaissance Ionique et Chimie de Coordination

We have previously investigated cis/trans isomerization processes in phenoxido-bridged mixed-valent Fe$^{II}$Fe$^{III}$ complexes that contain either one aniline or one anilide ligand. In this work, we compare the properties of similar complexes bearing one terminal protic ligand, either aniline or 1H-benzimidazole. Whatever the ligand, $^1$H NMR spectroscopy clearly evidences that the complexes are present in CH$_3$CN as a mixture of cis- and trans-isomers in a close to 1:1 ratio. We show here that addition of NEt$_3$ indeed allows the deprotonation of these ligands, the resulting complexes bearing either anilide or benzimidazolide that are coordinated to the ferric site. The latter are singular examples of a high-spin ferric ion coordinated to a benzimidazolide ligand. Whereas the trans-isomer of the anilide complex is the overwhelming species, benzimidazolide species are mixtures of cis- and trans-isomers in equal proportions. Moreover, cyclic voltammametry studies show that Fe$^{II}$Fe$^{III}$ complexes with 1H-benzimidazole are more stable than their aniline counterparts, whereas the reverse is observed for the deprotonated species.

Domaines: Chimie inorganique; Chimie de coordination

Eric Gouré, Michaël Carboni, Angélique Troussier, Patrick Dubourdeaux, Martin Clémancey, et al.. Deprotonation in mixed-valent diiron(II, III) complexes with aniline or benzimidazole ligands. Inorganic Chemistry, 2015, 54 (13), pp.6257-6266. ⟨10.1021/acs.inorgchem.5b00449⟩. ⟨hal-01211562⟩